Transparent conducting oxides

Abstract

The invention provides a transparent conducting film which comprises a compound of formula (I): Zn 1-x [M] x O 1-y [X] y (I) wherein: x is greater than 0 and less than or equal to 0.25; y is from 0 to 0.1; [X] is at least one dopant element which is a halogen; and [M] is: (a) a dopant element which is selected from: a group 14 element other than carbon; a lanthanide element which has an oxidation state of +4; and a transition metal which has an oxidation state of +4 and which is other than Ti or Zr; or (b) a combination of two or more different dopant elements, at least one of which is selected from: a group 14 element other than carbon; a lanthanide element which has an oxidation state of +4; and a transition metal which has an oxidation state of +4 and which is other than Ti or Zr. The invention further provides coatings comprising the films of the invention, processes for producing such films and coatings, and various uses of the films and coatings.

The invention claimed is: 
     
       1. A transparent conducting film which comprises a compound of formula (I):
   Zn 1-x [M] x O 1-y [X] y   (I)
 
 
       wherein:
 x is greater than 0 and less than or equal to 0.25; 
 y is from 0 to 0.1; 
 [X] is at least one dopant element which is a halogen; and 
 [M] is a combination of two or more different dopant elements, none of which is a group 13 element and one of which is Si and another of which is an alkali metal, an alkaline earth metal, a transition metal other than zinc, a p-block element other than a group 13 element, a lanthanide element or an actinide element. 
 
     
     
       2. A transparent conducting film according to  claim 1  wherein [M] is said combination of two or more different dopant elements, wherein [M] is a combination of:
 (i) Si; and 
 (ii) a transition metal, p-block or lanthanide element, which transition metal, p-block or lanthanide element has an oxidation state of +3, provided that the p-block element is other than a group 13 element. 
 
     
     
       3. A transparent conducting film according to  claim 1  wherein x is from 0.01 to 0.05. 
     
     
       4. A transparent conducting film according to  claim 1  wherein [X] is F and y is greater than 0 and less than or equal to 0.1. 
     
     
       5. A transparent conducting film according to  claim 1  wherein y is 0. 
     
     
       6. A transparent conducting film according to  claim 1 , which film has a resistivity, ρ, of less than or equal to about 4.0×10 −3  Ωcm. 
     
     
       7. A transparent conducting film according to  claim 1 , which film has a resistivity, ρ, of less than or equal to about 8.0×10 −4  Ωcm. 
     
     
       8. A transparent conducting film according to  claim 1  which has a mean optical transparency in the visible range of the spectrum of greater than or equal to about 75%. 
     
     
       9. A transparent conducting film according to  claim 1  which has a patterned structure. 
     
     
       10. A transparent conducting film according to  claim 1  which comprises two or more different layers. 
     
     
       11. A process for producing a transparent conducting film, which film comprises a compound of formula (I):
   Zn 1-x [M] x O 1-y [X] y   (I)
 
 
       wherein:
 x is greater than 0 and less than or equal to 0.25; 
 y is from 0 to 0.1; 
 [X] is at least one dopant element which is a halogen; and 
 [M] is a combination of two or more different dopant elements, none of which is a group 13 element and one of which is Si and another of which is an alkali metal, an alkaline earth metal, a transition metal other than zinc, a p-block element other than a group 13 element, a lanthanide element or an actinide element; 
 
       which process comprises producing said film by pulsed laser deposition. 
     
     
       12. A process according to  claim 11  which comprises:
 (a) providing a target material in a chamber, which target material comprises the elements Zn, O, [M] and optionally [X] wherein [M] and [X] are as defined in  claim 11 ; 
 (b) providing a substrate in the chamber; 
 (c) focusing a pulsed laser beam on the target material to generate a plasma; and 
 (d) depositing the plasma on the substrate to form the film. 
 
     
     
       13. A process according to  claim 12  wherein the target material is produced by heating a mixture of zinc oxide and an oxide of [M]. 
     
     
       14. A process according to  claim 13  wherein the mixture of zinc oxide and an oxide of [M] is heated at a temperature of from about 600° C. to about 1000° C. 
     
     
       15. A process according to  claim 12  wherein the target material is produced by:
 (a1) heating a solution comprising a zinc compound and a compound comprising [M]; 
 (a2) performing a solvent removal step; and 
 (a3) heating the resulting solid to produce said target material. 
 
     
     
       16. A process according to  claim 15  wherein the temperature of said heating in step (a1) does not exceed 200° C. and wherein the temperature of said heating in step (a3) does not exceed 500° C. 
     
     
       17. A process according to  claim 15  wherein said zinc compound is zinc citrate. 
     
     
       18. A process according to  claim 12  wherein the process further comprises (i) providing one or more further target materials in the chamber, which one or more further target materials are different from said target material which comprises Zn, O, [M] and optionally [X], and (ii) growing a multilayer film on said substrate by alternatively using the different target materials. 
     
     
       19. A process according to  claim 12  wherein step (d) of the process further comprises forming a patterned structure on the substrate. 
     
     
       20. A process according to  claim 12  wherein the plasma is deposited on only a portion of the surface of the substrate, in order to form a patterned film. 
     
     
       21. A process according to  claim 11  wherein the process further comprises subjecting the film to etching, thereby producing a patterned film. 
     
     
       22. A transparent conducting film obtained by a process for producing a transparent conducting film,
 which film comprises a compound of formula (I):
   Zn 1-x [M] x O 1-y [X] y   (I)
 
 
 
       wherein:
 x is greater than 0 and less than or equal to 0.25; 
 y is from 0 to 0.1; 
 
       [X] is at least one dopant element which is a halogen; and
 [M] is a combination of two or more different dopant elements, none of which is a group 13 element and one of which is Si and another of which is an alkali metal, an alkaline earth metal, a transition metal other than zinc, a p-block element other than a group 13 element, a lanthanide element or an actinide element; 
 
       and which process comprises producing said film by pulsed laser deposition. 
     
     
       23. A transparent conducting coating which comprises a transparent conducting film as defined in  claim 1 . 
     
     
       24. A transparent conducting coating according to  claim 23  which is an antistatic coating, an optical coating, a heat-reflecting coating, an antireflection coating, an electromagnetic interference shield, a radio-frequency interference shield, an electrowetting coating, or a coating for a display, for a touch panel or for a sensor. 
     
     
       25. An organic light-emitting device, an electroluminescent device, a solid-state light, a photovoltaic device, a solar cell, a photodiode, a transparent electronic device, an electrode, a display, a touch panel, a sensor, a window, flooring material, a mirror, a lens, a Bragg reflector, a strain gauge or a radio-frequency identification (RFID) tag which comprises a transparent conducting coating as defined in  claim 23  or a transparent conducting film as defined in  claim 1 . 
     
     
       26. A display as defined in  claim 25  which is a liquid crystal display, an electroluminescent display, an electrochrome display, a flat panel display, a plasma display, electronic paper or a field emission display. 
     
     
       27. A polymer or glass which is coated with a transparent conducting coating as defined in  claim 23 .